1. Field of the Invention
The present invention relates to processes for preparing cis-alkoxy-substituted spirocyclic 1-H-pyrrolidine-2,4-dione derivatives and alkali metal salts and alkaline earth metal salts thereof.
2. Description of Related Art
Alkoxy-substituted spirocyclic 1-H-pyrrolidine-2,4-dione derivatives of the general formula (I) having acaricidal, insecticidal and herbicidal action are known: EP-A 596 298, WO95/20572, WO 95/26954, WO 95/20572, EP-A 668 267, WO 96/25395, WO 96/35664, WO 97/01535, WO 97/02243, WO 97/36868, WO 98/05638, WO 99/43649, WO 99/48869, WO 99/55673, WO 01/74770, WO 01/96333, WO 03/035643, WO 04/007448, WO 04/065366, WO 04/111042, WO 05/066125, WO 05/049569, WO 05/044796, WO 05/092897, WO 06/056282, WO 06/056281, WO 06/029799, WO 07/096,058, WO 08/067,910, WO 08/138,551, WO 10/102,758.
Such compounds are usually prepared starting with the corresponding cis-substituted hydantoins of the formula (cis-II).

In the formulae (I), (II) and (cis-II),    V, W, X, Y and Z independently of one another represent hydrogen, alkyl, halogen, alkoxy, haloalkyl or haloalkoxy,    A represents C1-C6-alkyl,    G represents hydrogen (a) or represents one of the groups

in which    L represents oxygen or sulphur,    R1 represents in each case optionally halogen-substituted C1-C20-alkyl, C2-C20-alkenyl, C1-C8-alkoxy-C1-C8-alkyl, C1-C8-alkylthio-C1-C8-alkyl or poly-C1-C8-alkoxy-C1-C8-alkyl or represents optionally halogen-, C1-C6-alkyl- or C1-C6-alkoxy-substituted C3-C8-cycloalkyl in which optionally one or two not directly adjacent methylene groups are replaced by oxygen and/or sulphur, represents optionally halogen-, cyano-, nitro-, C1-C6-alkyl-, C1-C6-alkoxy-, C1-C6-haloalkyl-, C1-C6-haloalkoxy-, C1-C6-alkylthio- or C1-C6-alkylsulphonyl-substituted phenyl or represents thienyl,    R2 represents in each case optionally halogen-substituted C1-C20-alkyl, C2-C20-alkenyl, C1-C8-alkoxy-C2-C8-alkyl or poly-C1-C8-alkoxy-C2-C8-alkyl, represents optionally halogen-, C1-C6-alkyl- or C1-C6-alkoxy-substituted C3-C8-cycloalkyl or represents in each case optionally halogen-, cyano-, nitro-, C1-C6-alkyl-, C1-C6-alkoxy-, C1-C6-haloalkyl- or C1-C6-haloalkoxy-substituted phenyl or benzyl.
It is already known that in particular the cis-substituted compounds of the formula (I) have biologically advantageous properties (activity, toxicological profile) (WO2004/007448). Accordingly, there is an increased demand for cis-substituted hydantoins of the formula (cis-II) as starting materials.
However, owing to the preparation processes, the known compounds of the formula (II) are generally obtained in the form of cis/trans isomer mixtures.

It is also already known (WO2002/02532) that, from an isomer mixture of the formula (II), the desired cis isomer (cis-II) can be obtained in high purity by stirring the isomer mixture with aqueous ammonia, which apparently results in the formation of the ammonium salts of the formula (III). Since the solubility of the cis salts (cis-III) is considerably lower than that of the trans salts (trans-III), the salts (cis-III) or the hydantoins (cis-II) can be isolated in high purity by filtration.

However, this process has a number of disadvantages: the amount of ammonia required is high (multiple molar excess); the use of ammonia results in a drastically increased nitrogen load of the wastewater, which is unwanted and may require expensive work-up of the wastewater; the base strength of ammonia is insufficient for the subsequent hydrolysis of the hydantoin under temperature and pressure conditions acceptable for production on an industrial scale, so that direct further processing of (cis-III) is not possible.
Accordingly, there was still a need for a process for separating isomers of compounds of the formula (II), which process is simpler, better to realize on an industrial scale and more environmentally friendly.